Posted
by
Zonk
on Saturday December 01, 2007 @05:26PM
from the you-in-the-back-speak-up dept.

palegray.net writes "Wired reports on new research into the phenomenon of 'silenced genes', genetic constructs that have no 'partner' in case one goes wrong over the course of your lifetime. Scientists at Duke University have mapped some 200 genes that may 'play a profound role' in the health of the average human. 'Many of the newly found imprinted genes are in regions of chromosomes already linked to the development of obesity, diabetes, cancer and some other major diseases, the researchers reported ... Scientists had thought imprinted genes would account for about 1 percent of the human genome. While scientists must double-check that the newly identified ones are truly silenced, the new map matches that tally.'"

Usually, people inherit a copy of each gene from each parent and both copies are active, programmed to do their jobs whenever needed. If one copy of a gene becomes mutated and quits working properly, often the other copy can compensate.

Genetic imprinting knocks out that backup. It means that for some genes, people inherit an active copy only from the mother or only from the father. Molecular signals tell, or "imprint," the copy from the other parent to be silent.

I believe that understanding epigenetics [wikipedia.org] will have a huge impact on human medicine. If we learn how to turn different genes on and off we could do all sorts of amazing things. It's already clear that a number of health problems are related to having a gene in the wrong state.

you're missing the point entirely. This isn't just a few cells that are affected, this is your entire population of cells. if you inherit a gene from your father that is "switched off" and that gene is the only one that can be inherited [only from Y chromosome for example] then you're kind of screwed. There isn't a second copy that is switched on and functional to prevent the associated disease caused by the first gene being switched off. There are a lot of these kind of genes that are regulated in the levels of expression and on/off states of the gene. Hardly mundane.

Completely irrelevant. Unless you are in a position to DO something about it. We already know there are many lethal gene combinations, that produce in utero abortion or neonatal death. Your point is?

Now if you could point out a case of a single gene being altered AFTER embryogenesis (by environmental factors or whatever) that produces disease, then we're talking about eventually being able to work on a way of preventing this. However as far as I kno

(a) It helps provide people with genetic counseling e.g. helps in deciding if you want to continue with a pregnancy if you know that your fetus has a genetic defect on the paternal copy (and the maternal copy is silenced) by sequencing an amniocentesis sample.

(b) More fundamental to this is that, is that this might help pin down a gene defect as the cause of a disease. For example you might find some locus often associated with a disease but in the patients you sequence the genes, it turns out one of them has got a perfect copy and the other has a mutation. Since it is difficult to say for a majority of mutations if they would affect function or are simple polymorphisms in the population, you continue searching other genes. OTOH, if you know one of the copies is shut down, and you see one copy has a mutation, you promptly analyze this candidate gene a lot more.

(c) Finally, of course for proper cure, it helps to know what the defect is. e.g. if you know it is a defect in an ion transporter, you might try some types of drugs and if it is an inflammatory defect you will try something else - so (b) is useful in guessing plus making animal models to test them.

(d) there is the hope that one day we will be able to fix things gene therapy which again is dependent on figuring out the molecular defect by (b).

Scientists are searching for small molecules that can have epigenetic effects of switching genes off or on. So these new epigenetic maps of active and silenced genes can help guide research on which genes to target for small molecule therapy. Also, RNA interference (RNAi) is another method for genetic activation/deactiviation, and as that technique improves, it may be possible to use it for therapeutic medicine in humans.

While perhaps you might also be able to identify non-desirable traits that are more likely to be passed on to offspring

This, IMO, could be incredibly valuable alone. For example, I have Crohn's Disease, and knowing that it's very likely that there's a genetic component to my condition, I would never even consider having biological children; even if the chance that they'd inherit it from me is fairly small, IMO, given the effects of this disease, it's completely irresponsible for me to consider having a chil

Fifteen years ago I found out that I had inherited Ankylosing Spondylitis from my father. I saw the pain that he suffered from and I know that I will one day also have similar problems. I took the decision that I wouldn't have any children, it hasn't been easy. I've lost several potential wives in recent years, which I greatly regret.
I heard a programme on the BBC Radio 4, one afternnon on the way home from work. It's a weekly 30 minute science show, this week three scientist were bubbling with enthusiasm

Now if you could point out a case of a single gene being altered AFTER embryogenesis (by environmental factors or whatever) that produces disease, then we're talking about eventually being able to work on a way of preventing this. However as far as I know, altering the gene in a single cell will damage THAT cell only. Now with the exception of the cancers (which I made in my previous post) please point out a disease resulting from a mutation of a single cell?

IANAB, but perhaps you're overlooking environmental factors that influence gene expression and are potentially damaging to normal cellular functions. Also, cancers and oncogenes would be the rule rather than the exception as it is notorious for doing the exact kind of thing this research is aiming to treat. Think if you will, of a smoker who's been dumping craploads of toxins and mutagens onto his/her lung tissue for years at a time. It won't be just one or two cells that mutate or die. Also, if the gene that fails happens to be in one or two of those bone marrow cells that are responsible for churning out blood cells and/or maintaining your immune system, you're risk of developing leukemia increases dramatically. Because since cancer is essentially uncontrolled cell growth, it will quickly overwhelm any normal body functions if not stopped.

you are correct, the gist of the research goes like this:1) some genes can be switched on or off by environmental factors [chemicals, other genes etc.]2)if one of these cells that has a switched on/off gene just happens to be a sperm cell or an egg, it can carry that epigenetics to the next generation.3) some genes can only be inherited functional from one parent4) if that parent happens to be the one that has the inactivated [switched off] gene then that gene is entirely non-functional in the offspring because there is no functional back up gene from the other parent.this leads to the conclusion that environmental factors can alter gene expression which can be inherited to offspring which under some conditions and genes no longer have a functional gene that may or may not prevent disease, that is to say if the gene is inactivated you're likely to get the associated disease. In many cases, these genes are thought to be involved in obesity, heart disease, cancer etc. which means that environmental factors in your parent's lives or even your grandparent's may contribute to you being more likely to get a certain disease associated with a non-functional gene.

I wonder how much two way transfer there is between bacteria, viruses and human genes. We know the bacteria are far from static targets, and some of them definitely have the ability to influence your genes (in particular ones that hijack cells like cell wall deficient bacteria) and vice versa. We see far higher rates of certain "autoimmune" diseases in health care workers, likely for this reason. But it might point out another factor in why they get sick and another health care worker exposed to the same o

As you said, you are not a biologist. Leukemia is a type of cancer, and I specifically excluded cancer in my post. This research may be relevant to cancer (ONLY, in my opinion). However it's not the Holy Grail it is presented as.There are many stem cells in the bone marrow and wiping one of those cells out will not lead to aplasia. And we're talking about millions of cells getting the exact same gene damaged - in theory. Now what are the odds of THAT?

As you said, you are not a biologist. Leukemia is a type of cancer, and I specifically excluded cancer in my post. This research may be relevant to cancer (ONLY, in my opinion). However it's not the Holy Grail it is presented as.

If this leads to advancement in the treatment of cancer (even if only cancer), I think many would consider it to be a holy grail enough. But then, to the credit of the article's author, no where in the article did they allude to this research result being a Panacea for all of hum

Sometimes imprinting goes awry before birth, leaving a normally silenced gene "on" or silencing one that should not be....
Now a question is how imprinting may be changed to reactivate an imprinted gene after birth.

If you had no plan on applying genetic research, there would be no worldly reason to perform the research in the first place. Sure, Science for Science's sake is fun, but I'm sure a 1000x1000 grid Sudoku puzzle that used every known symbol would be just as consuming/fulfilling. More to the point, if you want further high-level research you need financial backing (Investors usually invest in projects that have a chance of a positive return).

or gene replacement therapy, which means that you could become a clone of anyone's genes that you could get your hands on..... as well as reactivating the genes with HGH therapy and shooting yourself through a 2nd growth stage that would make you younger..... c'mon what 90 year old man wouldn't like to be an 18 year old paris hilton

Not all genes are expressed by both the maternal and paternal lines. Some genetic defects are caused because both copies express themselves when one should be turned off. I'm sure the controls and implications will turn out to be more complicated than we know. But this is just another area where all the heat is epigenetic.

Presumably this natural imprinting occurs when the DNA gets reprogrammed during fertilization. The de-methylation and re-methylation determines which sequences get turned off. The attempts at cloning using somatic nuclear tranfers skip this crucial step and are found to have different methylation patterns than natural cells. This leads to defective imprinting that may be the cause of the anomolies found in Dolly and others and may be the cause of the abnormally large offspring of clones as they are over-expressing some genes and have others turned off that should be on.

On the Duke news site [duke.edu] they give more information about how they came to their findings. They mention that they fed data about the sequences of genes known to be imprinted, and likely to be non-imprinted genes into a computer to check for differences. Based on that, they searched for other sequences that resembled the imprinted ones. That's why the results are just good guesses and more research need to be done to determine if they are true positives.

Like most articles on Science in the popular press, this article is oversimplified to the point of not being true anymore.Epigenetics is a relatively new field that deals with several new layers of the language of DNA that are only recently beginning to be understood. The 2007 Nobel Prize in Physiology or Medicine went to Fire and Mello for their work in uncovering a phenomenon known as RNA interference that is a key part of epigenetic inheritance.

From TFA: "Previous work by Jirtle and others shows the environment can reprogram how some genes operate, making them speed up or slow down or work at the wrong time. In a groundbreaking 2003 experiment, Jirtle fed pregnant mice different nutrients to alter the coat color of their babies. The feed affected chemical signals that control how hard a certain gene worked, determining when the babies had yellow coats like mom or brown ones."

No - Lamarck fabricated most of his results. Different levels of gene expressions have been known about since the start of genetics itself, usually they are accounted for via statistics (gene expression as a probability rather than a certainty). The environmental effects on genetics are very different from Lamarckian concepts. It's more unexpressed potential, rather than a primarily environmental driven process the Russians thought they had uncovered.